1. Technical Field
This invention relates to nonionic splittable surfactants and their use in industrial, commercial, and institutional applications which process aqueous streams, typically effluent streams, bearing water-insoluble, oily or waxy contaminants/impurities, including fats, oils and grease (FOGs), total petroleum hydrocarbons (TPHs), and other such hydrophobic materials. This invention provides compostitions and methods designed to allow treatment of said aqueous streams to remove such hydrophobic materials. These aqueous streams generated during processing contain said contaminants which are held in the form of a relatively stable emulsion by the action of said surfactants. The contaminants may be removed from the aqueous effluent by acidifying the waste water, resulting in a release of said contaminants. Specific examples of said effluents include spent laundry wash water, contaminated oil/water emulsions from metalworking processes, aqueous streams from textile dyeing, aqueous wash streams from metal (vehicle) cleaning operations, waste or recycle streams from deinking processes, etc.
2. Discussion of the Prior Art
Direct discharge of contanminants or discharge of contaminants to a Public Owned Treatment Works (POTW) presents significant problems to numerous industries, e.g., industrial laundries, metalworking, food processing, metal cleaning, etc., which generate large volumes of aqueous effluents containing FOG, TPH, and/or other emulsified oils (organics) commonly referred to as oily waste-water. Discharge of aqueous waste steams to a POTW or direct disposal of wash solutions into waterways, must be done in compliance with environmental regulation standards. In order to meet these requirements, the waste stream generally undergoes pretreatment to reduce the contaminants (e.g., FOGs, TPHs, etc.) so discharge compliance may be accomplished. In the case of industrial laundry operations, this problem is of particular concern as large volumes of laundry waste-water are generated containing a variety of contaminants. These contaminants are removed from the soiled fabrics during the wash process and become associated with the surfactant utilized to hold the impurities in aqueous solution to form relatively stable emulsions.
Metalworking fluids are used to provide cooling and lubrication during the many cutting, grinding and forming operations that are used during processing. Metalworking formulations are complex mixtures which contain additives to perform various functions, e.g., emulsification, corrosion inhibition, lubrication, coupling, defoaming, wetting, dispersing, etc. Surfactants are primarily used in metalworking formulations as emulsifiers, wetting agents and corrosion inhibitors. In order to minimize the discharge and the need for waste treatment (cost savings), the fluids are constantly recycled for an extended time. After a period of use, however, the effectiveness of the metalworking fluids becomes significantly less due to contaminants which are introduced to the fluid from the process operations. These include such impurities as machine oil (often referred to as tramp oil), metal particles, anionic salts, cations, and other foreign matter which have collected in the metalworking fluid. These fluids are then discharged to holding tanks whereby numerous treatment technologies are employed to remove oils (some of which are recycled) and greases to allow the aqueous phase to meet the required local pretreatment ordinances (typically oil and grease concentrations of less than 100 mg/l). One of the treatment technologies involves chemical emulsion (oil/water)-breaking, whereby an emulsion-breaking agent e.g., alum or a polyelectrolyte, is added to facilitate phase separation. This process works by neutralizing electrical charges which aid in the emulsification of the oil droplets. Typically, anionic surfactants (those surfactants bearing a negatively charged ion which carries the surface active properties), e.g., soaps, petroleum sulfonates, and the like, are used in metalworking formulations due to this ability to be charge neutralized (thus destroying surfactant properties). Anionic surfactants have undesirable properties, e.g., foaming and lack of hard-water stability vis-a'-vis nonionic surfactants; however, nonionic surfactants bear no charge and are not amenable to this type of chemical emulsion-breaking.
Hard surface cleaning formulations are used to clean hard, usually smooth surfaces, e.g., metals, ceramics, etc., of process fluids, oil, dirt, debris, etc. Alkaline cleaners are commonly used for aqueous systems and surfactants are used as wetting agents and dispersants. Hard surface cleaning may be done by immersion or spraying. The surfactants should be stable to an alkaline pH and be low foaming. After several cleaning operations, the cleaning chemicals have accumulated sufficient contaminants (e.g., oils) to limit the effectiveness of the surfactant to remove them from the cleaned surfaces, e.g., metal parts, ceramic tiles, and the like, and prevent redeposition (through emulsification). Additional surfactant may be added to mitigate this problem; however, the additional surfactant increases the likelihood of undesirable foam generation, and makes waste treatment (oil/water emulsion) more difficult when the bath is discarded. Alkylphenol ethoxylates (e.g., Triton.RTM. X-100, sold by Union Carbide Corp., Danbury, Conn.) are known to be good surfactants for metal cleaning operations; however, these materials are difficult to waste-treat since they are nonionic.
Deinking formulations are used to remove printing ink from old newspapers, magazines, business paper, etc. In one of the processes, referred to as the "washing" process, the printed waste paper is fiberized in an alkaline environment, under elevated temperatures, and mechanical stirring in the presence of deinking formulations. Various washing stages are employed to obtain a thick suspension of pulp fibers that are largely free of ink. Surfactants are used in deinking processes as wetting agents to aid in dispersing the inks and binders, and as emulsifiers. Alkylphenol ethoxylates and primary and secondary fatty alcohol ethoxylates are commonly used due to low foaming and good dispersion properties. Effluent from the washing process which contains these surfactants has emulsions/dispersions (e.g., ink in water) which must be waste-treated. Additionally, recycled water streams from the process need to be treated.
The textile industry also generates several waste water effluent streams from their processes. For example, during scouring (a cleaning process) of man-made fibers, surfactants are added to remove chemical adjuncts (e.g., lubricant oil) which remain on the fiber. Surfactants are used for detergency and dispersion of the scoured-off particles. Alkylphenol ethoxylates are commonly used due to low foaming and good dispersion properties. Effluent from the washing process which contains these surfactants has emulsions (e.g., oil in water) which are difficult to waste-treat. In addition, in a dispersion dyeing process, surfactants are employed to disperse the water-insoluble dyes to ensure uniform distribution in the dye bath. When these baths must be discarded, the resultant dispersions are difficult to waste-treat.
In a process known as tertiary oil recovery, oil deposits which remain after primary and secondary oil recovery are extracted. In the chemical flooding of the deposits, chemicals are added to water to aid in the recovery. Among these are surfactants which are used to reduce the interfacial tension between the oil and the water. Thus, the surfactant (and sometimes a co-surfactant) generates an emulsion with the crude oil and the water, which allows the oil to be removed from the deposit. In a micellar flooding process the surfactant with crude oil is pumped into the oil deposit for several days to extract additional crude oil. Generally, anionic surfactants (e.g., petroleum sulfonates, ether sulfates, ether carboxylates, etc.) are employed.
The above-mentioned uses for the compounds described hereinafter in the instant invention are not intended to be exclusive, but rather to illustrate the problem and the need for this invention for industrial, institutional, and commercial processes which generate aqueous waste streams containing FOGs, TPHs, and other water-insoluble contaminants which are emulsified due to the presence of surfactants.
One of the desirable properties of an effective surfactant is to efficiently emulsify water insoluble components. However, the separation of these components which might now be considered impurities and other contaminants from the aqueous effluent is complicated by the emulsifying property of the surfactant. Therefore, the stronger or more efficient the surfactant in removing and suspending hydrophobic compounds in aqueous solution, the more difficult is the later separation of the hydrophobic impurities from the water.
What is needed by businesses and industries utilizing surfactants in process streams which are eventually discharged to the environment is a highly effective surfactant which first may be utilized as a conventional surfactant to emulsify hydrophobic agents and suspend them in water, and then is capable of modification so as to permanently reduce or remove its surfactant ability and permit release, separation, and collection of the previously suspended hydrophobic constituents associated with the surfactant.
This problem has been addressed in the industrial laundry industry in part by the use of amine-based surfactants and various improved processes based on their use. These processes are generally characterized by treatment of the aqueous stream bearing the amine-based surfactant with the emulsified hydrophobic contaminants with an acid to deactivate the surfactant and release the hydrophobic contaminants, which then agglomerate and are removed, usually by a skimming or other physical separation process. Typical processes are disclosed in U.S. Pat. Nos. 5,076,937; 5,167,829; 5,207,922; and 5,374,358, among others. Amine-based surfactants have not proven to be fully satisfactory, however, since their detergency is below the best surfactants commonly used in laundry applications, e.g., nonyl phenol ethoxylates (NPE), generally considered to be the standard of the industry. Moreover, the amine-based surfactants tend to re-form and regain their surfactancy when the pH is raised, e.g., to neutralize the stream prior to discharge to a POTW which may cause problems downstream (e.g., foaming).